1. Field of the Invention
The present invention relates to a sheet with plate springs to be used, for example, as a thin operating panel in such an electronic device as a portable telephone set or a video camera, as well as a switch device using the same.
2. Description of the Prior Art
With a panel switch as an example, a conventional sheet with plate springs and a conventional switch device using the conventional sheet with plate springs will be described with reference to FIGS. 10 to 12, of which FIG. 10 is an exploded perspective view of a conventional sheet with plate springs, FIG. 11 is a sectional view taken on line XIxe2x80x94XI in FIG. 10, and FIG. 12 is an explanatory diagram explaining how to assemble a conventional switch device using the conventional sheet with plate springs.
The construction of a conventional sheet with plate springs will now be described with reference to FIGS. 10 and 11. Plural movable contacts 31 are each constituted by a thin, dome-like, metallic plate spring and can be displaced with click feeling when a depressing force is exerted thereon from its top portion.
Film 32 is a generally rectangular, large-sized, somewhat thick film with an adhesive layer affixed to a lower surface thereof. The film 32 has plural holes 32a which are formed through upper and lower surfaces of the film and which are each a little larger than each movable contact 31.
The movable contacts 31 are respectively inserted into the holes 32a. 
A plurality of generally square adhesive sheets 33, which are each a little larger than each hole 32a, are each constituted of a film with an adhesive layer affixed to the whole of its lower surface and are each formed with a through hole 33a generally centrally of one side of the sheet and in the vicinity of the side edge.
Each adhesive sheet 33 is affixed to an upper surface of each movable contact 31 and also affixed to the surface portion of the film 32 contiguous thereto, thereby fixing the movable contact 31 to the film 32 and holding it on the film.
The through holes 33a are respectively opposed to the holes 32a of the film with the movable contacts 31 received therein to provide communication of the holes 32a with the exterior.
A separator 34 is formed by a large-sized film or paper having substantially the same shape as the film 32. The separator 34 is affixed to the lower surface of the film 32 through the adhesive layer formed on the film lower surface to protect lower surfaces of the movable contacts 31 so that dust and other foreign matters may not get into the interior of each movable contact dome. In this way there is constituted a sheet 35 with movable contacts (a sheet with plate springs).
A conventional switch device and how to assemble it will now be described with reference to FIG. 12. The conventional switch device uses the conventional sheet 35 with movable contacts (sheet with plate springs) and includes a large-sized insulating substrate 36. The insulating substrate 36 is a flexible substrate constituted of a polyimide film for example, and first and second fixed contacts 36a, 36b are formed on the surface of the insulating substrate 36, for example, by etching copper foil or the like.
The adhesive layer applied to the lower surface of the film 32 in the sheet 35 with movable contacts is exposed by releasing the separator 34 affixed to the film lower surface, allowing the holes 32a to be opposed to the first and second fixed contacts 36a, 36b, and in this state the film 32 is affixed to an upper surface of the insulating substrate 36 to assemble a switch device.
In this state, the movable contacts 31 are placed on the surface of the insulating substrate 36 in such a manner that the peripheral edge of a lower end portion of each movable contact 31 is constantly in contact with the associated second fixed contacts 36b and that the dome-like top of each movable contact 31 is spaced from and opposed to the associated first fixed contact 36a. 
Next, the operation of the conventional switch device constructed as above will be described. If an operator depresses the adhesive sheet 33 located above a movable contact 31 through an operating member (not shown), an upper portion of the movable contact 31 is inverted concavely and comes into contact with the associated first fixed contact 36a to turn ON between the first and second fixed contacts 36a, 36b. 
At this time, the air present within the dome of the movable contact 31 flows out from an end portion of the movable contact 31, then passes through the associated hole 32a formed in the film 32 and further through the through hole 33a formed in the associated adhesive sheet 33, and escapes to the exterior.
Upon release of the depressing force, the upper portion of the movable contact 31 leaves the first fixed contact 36a, thus turning OFF between the first and second fixed contacts 36a, 36b. 
At this time, air flows into the dome through the through hole 33a formed in the adhesive sheet 33.
However, since the conventional sheet with plate springs requires the film 32 for insertion therein of the movable contacts 31 formed of plate springs and also requires the adhesive sheets 33 for fixing the movable contacts adhesively, the number of components used is large to result in an increase of cost.
In addition, since the adhesive sheets 33 are affixed to the movable contacts 31 (plate springs) one by one, considerable time and labor are required for the affixing work, thus giving rise to the problem that the productivity is low.
Moreover, since the holes 32a formed in the film 32 are directly connected to the exterior through the through holes 33a formed in the adhesive sheets 33, dust and other foreign matters are apt to get into the holes 32a from the exterior.
Further, in the conventional switch device using the conventional sheet with plate springs, not only dust and other foreign matters are apt to get into the holes 32a of the film 32 from the exterior because the holes 32a are in direct communication with the exterior, but also in the case where electronic parts are mounted on the insulating substrate 36, the electronic parts become more likely to be destroyed by static electricity charged on the hands and fingers of the operator.
Further, since the film 32 having holes 32a for fitting therein of the movable contacts 31 (plate springs), as well as plural adhesive sheets 33, are required, the productivity is low, the number of components used increases, the cost becomes high, and the thickness of the switch device increases.
It is an object of the present invention to provide a sheet with plate springs capable of preventing the entry of dust and other foreign matters from the exterior and which is inexpensive, as well as a switch device capable of preventing the entry of dust and other foreign matters from the exterior and which is thin and strong against static electricity.
According to a first apparatus adopted by the invention for solving the above-mentioned problems there is provided a sheet with plate springs, comprising an adhesive sheet having adhesive portions on one side thereof, a plurality of plate springs each constituted of a deformable metallic plate having resilience and with the adhesive portions affixed to upper surfaces thereof, and a sheet-like separator affixed to the adhesive sheet to protect lower surfaces of the plate springs, wherein the one side of the adhesive sheet is studded with the adhesive portions each in a projected form, and vent portions are formed between the studded and projected adhesive portions and between the plate springs and the exterior of the adhesive sheet so that air can get into and out of the vent portions.
According to a second apparatus adopted by the invention there is provided, in combination with the above first apparatus, a sheet with plate springs wherein the total area of the adhesive portions studded and projected on the one side of the adhesive sheet is larger than the total area of the one side portion of the adhesive sheet where the adhesive portions are not projected.
According to a third apparatus adopted by the invention there is provided, in combination with the above first apparatus, a sheet with plate springs wherein the area of each of the studded and projected adhesive portions is smaller than the area of the upper surface of each of the plate springs.
According to a fourth apparatus adopted by the invention there is provided, in combination with the above third apparatus, a sheet with plate springs wherein the spacing between adjacent studded and projected portions of the adhesive is smaller than the size of each of the plate springs.
According to a fifth apparatus adopted by the invention there is provided, in combination with the above first apparatus, a sheet with plate springs wherein the adhesive portions are colored.
According to a sixth apparatus adopted by the invention there is provided, in combination with the above first apparatus, a sheet with plate springs wherein the projected adhesive portions each have a polygonal shape and are arranged regularly.
According to a seventh apparatus adopted by the invention there is provided, in combination with the above sixth apparatus, a sheet with plate springs wherein the projected adhesive portions each have a hexagonal shape.
According to an eighth apparatus adopted by the invention there is provided, in combination with the above first apparatus, a sheet with plate springs wherein the projected adhesive portions each have a generally circular shape and are arranged regularly.
According to a ninth apparatus adopted by the invention there is provided, in combination with the above first apparatus, a sheet with plate springs wherein either the adhesive sheet or the separator is made transparent or translucent and the other is made opaque.
According to a tenth apparatus adopted by the invention there is provided a switch device comprising an adhesive sheet whose lower surface is studded with adhesive portions, movable contacts constituted by a plurality of plate springs whose upper surfaces are affixed to the adhesive portions, the plate springs each being constituted of a deformable metallic plate having resilience, and an insulating substrate having a plurality of fixed contacts, wherein the adhesive portions studded and projected on the lower surface of the adhesive sheet are affixed to the insulating substrate in a state such that the movable contacts affixed to the adhesive sheet through the adhesive portions are opposed to the fixed contacts of the insulating substrate, and vent portions are formed between the studded and projected adhesive portions and between the movable contacts and the exterior of the adhesive sheet so that air can get into and out of the vent portions.
According to an eleventh apparatus adopted by the invention there is provided, in combination with the above tenth apparatus, a switch device wherein the total area of the adhesive portions studded and projected on the lower surface of the adhesive sheet is larger than the total area of the lower surface portion of the adhesive sheet where the adhesive portions are not projected.
According to a twelfth apparatus adopted by the invention there is provided, in combination with the above tenth apparatus, a switch device wherein the area of each of the studded and projected adhesive portions is smaller than the area of the upper surface of each of the movable contacts.
According to a thirteenth apparatus adopted by the invention there is provided, in combination with the above tenth apparatus, a switch device wherein the projected adhesive portions each have a polygonal shape and are arranged regularly.
According to a fourteenth apparatus adopted by the invention there is provided, in combination with the above thirteenth apparatus, a switch device wherein the projected adhesive portions each have a hexagonal shape.
According to a fifteenth apparatus adopted by the invention there is provided, in combination with the above tenth apparatus, a switch device wherein the projected adhesive portions each have a generally circular shape and are arranged regularly.
According to the fifteenth solving means adopted by the invention there is provided, in combination with the above tenth means, a switch device wherein the projected adhesive portions each have a generally circular shape and are arranged regularly.